Tanjiro had noticed Zenitsu flirting with you more and more often, he could t help but feel jealous. He wanted your attention, and he wanted to give you all of the attention and affection he possibly could. He was such a kind and loving boyfriend, but his jealously can get in the way sometimes.

Zenitsu: Smiling flirtatiously. You look good today, but I bet you would look even better up close~

Tanjiro: Zenitsu, watch it. You know she’s mine.